Engines, for example vehicle engines, are being downsized and boosted, which is reducing the available vacuum from the engine. This vacuum has many potential uses, including use by the vehicle brake booster.
One solution to this vacuum shortfall is to install a vacuum pump. Vacuum pumps, however, have a significant cost and weight penalty to the engine, their electric power consumption can require additional alternator capacity, and their inefficiency can hinder fuel economy improvement actions.
Another solution is an evacuator that generates vacuum by creating an engine air flow path that is parallel to the throttle, referred to as an intake leak. This leak flow passes through a Venturi that generates a suction vacuum. The problem with the presently available evacuators is that they are limited in the amount of vacuum mass flow rate they can generate, and by the amount of engine air they consume.
A need exists for improved designs that generate increased suction mass flow rate, in particular when the motive flow is a boosted motive flow.